A space shooter from Gremlin Graphics, released for the Amstrad CPC and the Commodore 64.

From box back (C64 release)
Only the elite pass the three phase test of the Corps of Guardian Warriors – co-ordinated fury in destruction of the mutant hordes of the underworld; supreme command skills in frantic defence against the invading alien space fleets and merciless nerve in bloody battle against the monster of the Pit of Despair. Then the final chilling decision – enter the Metamorphosis Chamber to fuse lifeforms with your vanquished foe or face your next challenge with only the powers your mortal form bestows on you.